Question

Helpp

Answer 1

@jim_thompson5910 @Nameless

Answer 2

sin(3x) = sin(2x + x)


sin(3x) = sin(2x)cos(x) + cos(2x)sin(x)


sin(3x) = sin(x+x)cos(x) + cos(x+x)sin(x)


sin(3x) = [sin(x)cos(x) + cos(x)sin(x)]cos(x) + [cos(x)cos(x) - sin(x)sin(x)]sin(x)


sin(3x) = [2cos(x)sin(x)]cos(x) + [cos^2(x) - sin^2(x)]sin(x)


sin(3x) = 2cos^2(x)sin(x) + cos^2(x)sin(x) - sin^3(x)


Do the same to find cos(3x)

Answer 3

I'm using the identities


sin(x+y) = sin(x)cos(y) + cos(x)sin(y)

cos(x+y) = cos(x)cos(y) - sin(x)sin(y)

Answer 4

sry i should have gone further

sin(3x) = 3cos^2(x)sin(x) - sin^3(x)

Answer 5

im confused can you tell me what the answer is so i can check if i got it right?

Answer 6

hold on one sec

Answer 7

checking the answer, but the second one doesn't seem right, but one sec

Answer 8

ok thank you

Answer 9

well using a graphing calculator, I was able to eliminate choices A through C

so that leaves D